Gas-Treatment Devices

ABSTRACT

An HME has exchange elements ( 4 ) at opposite ends of a tubular housing ( 1, 101 ) and a central port ( 2 ) for connection to a tracheal tube ( 3 ). An oxygen port ( 5, 105, 105 ′) is located centrally with the major part of it being contained within a recess ( 40, 140, 140 ′) on the exterior of the housing and extending at right angles to the length of the housing. The oxygen port ( 5, 105, 105 ′) opens into a wider passage ( 32, 32 ′) extending within the housing, which opens on the external face ( 30 ) of the two exchange elements ( 4 ). A large suction aperture ( 60 ) aligns with the port ( 2 ) opening to the tracheal tube ( 3 ) and is covered by a hinged flap ( 61 ) when not in use.

This invention relates to gas-treatment devices of the kind having ahousing, a first port adapted for connection to a patient breathingdevice, a gas-treatment element through which gas can flow in bothdirections to and from the patient and a second, oxygen supply port bywhich oxygen can be supplied to the patient via the gas-treatmentdevice, the oxygen supply port being in the form of a tubular stem.

The invention is more particularly, but not exclusively, concerned withheat and moisture exchangers (HMEs) of the kind connected to a patientbreathing device.

Where a patient breathes through a tube inserted in the trachea, such asa tracheostomy or endotracheal tube, gas flow to the bronchi is notwarmed and moistened by passage through the nose. Unless the gas iswarmed and moistened in some way it can cause damage and discomfort inthe patient's throat. The gas can be conditioned by a humidifier in theventilation circuit but, most conveniently, a heat and moisture exchangedevice (HME) is used. HMEs are small, lightweight devices including oneor more exchange elements, such as of a paper or foam treated with ahygroscopic substance. When the patient exhales, gas passes through theexchange element and gives up a major part of its heat and moisture tothe element. When the patient inhales, gas passes through the exchangeelement in the opposite direction and takes up a major part of the heatand moisture in the exchange element so that the gas inhaled by thepatient is warmed and moistened. These HMEs are low cost and disposableafter a single use so do not require cleaning or present any crosscontamination risk. They can be connected in a breathing circuit orsimply connected to the machine end of a tracheal tube and left open toatmosphere where the patient is breathing spontaneously.

HMEs are sold by Smiths Medical International Limited of Hythe, Kent,England under the Thermovent name (Thermovent is a registered trade markof Smiths Medical International Limited), by Hudson RCI AB under theTrachVent name (TrachVent is a registered trade mark of Hudson RCI AB),by DAR, Medisize, Intersurgical and other manufacturers. HMEs ofteninclude an oxygen inlet port to which an oxygen supply tube can beconnected. This enables supplementary oxygen to be administered to thepatient via the HME. Advantageously, the oxygen port opens on the sideof the HME element remote from the patient so that the oxygen has topass through the HME element before reaching the patient. Examples ofHMEs with oxygen supply ports are described in GB 2391816, WO 01/72365,U.S. Pat. No. 5,505,768, SE 516666, U.S. Pat. No. 3,881,482, DE20302580, DE 20114355U, WO 97/01366, US 2002/0157667, U.S. Pat. No.6,422,235, EP 1208866 and U.S. Pat. No. 4,971,054.

Because the HME is often connected to the end of a tracheal tube it isdesirable that its construction be as compact as possible.

It is an object of the present invention to provide an alternativegas-treatment device.

According to one aspect of the present invention there is provided agas-treatment device of the above-specified kind, characterised in thatthe housing has a recess on its external surface, and that the majorpart of the oxygen supply port extends within the recess when not inuse.

The device preferably has two gas-treatment elements at opposite ends ofthe housing. The oxygen supply port may be located intermediate the endsof the housing. The or each gas-treatment element may be an HME exchangeelement. The housing preferably has an elongate shape and the portpreferably extends at right angles to the axis of the housing. Theoxygen supply port may be displaceable from a first position in which amajor part of the port is contained within the recess and a secondposition in which it projects from the recess for connection of anoxygen supply tube. The port may be displaceable by rotation or bysliding. The housing may have a suction aperture located substantiallyopposite the first port, the suction aperture being covered by a flapthat can be displaced to enable a suction catheter to be extendedthrough the suction aperture into the patient breathing device. Anoxygen supply passage preferably extends along the housing and opensonto an external face of the or each gas-treatment element, the oxygensupply port being directed at an angle to the oxygen supply passage suchthat oxygen flow changes direction where it emerges from the port intothe passage, and the cross-sectional area of the oxygen passage beinggreater than that of the oxygen port so that oxygen pressure drops whereit emerges from the port into the passage.

An HME according to the present invention will now be described, by wayof example, with reference to the accompanying drawings, in which:

FIG. 1 is a perspective side view of the HME connected to the end of atracheostomy tube;

FIG. 2 is a perspective end view of the HME;

FIG. 3 is view of the lower side of the HME;

FIG. 4 is a cross-sectional view of a part of the HME;

FIG. 5 is a perspective view of an alternative HME with its oxygen portstowed;

FIG. 6 is a side elevation view of the HME of FIG. 5 with the oxygenport extended;

FIG. 7 is a view of the underside of the HME of FIG. 5 with the oxygenport extended;

FIG. 8 is a cross-sectional view of the HME with the oxygen portextended; and

FIG. 9 is a side elevation view of a second alternative, modified HME.

With reference first to FIGS. 1 to 4, the HME has an outer housing 1with a coupling or port 2 by which it is connected to a tracheal tube 3.The housing 1 supports two heat and moisture exchange elements 4 atopposite ends by which gas supplied to the patient is warmed andmoistened. An oxygen supply port 5 is mounted on the housing 1 to enablesupplementary oxygen to be supplied to the patient when necessary.

The housing 1 is generally cylindrical and is moulded from a rigidplastics material. The patient coupling 2 projects radially outwardly ofthe housing midway along its length and has an internal tapered surface20 adapted to connect to a standard male tapered coupling 21 on the endof the tracheal tube 3. The coupling 2 opens to the interior 22 of thehousing 1 in communication with the inner surface of the exchangeelements 4.

The exchange elements 4 are each conventional, being in the form of adisc comprising a spiral roll of corrugated paper treated with ahygroscopic salt to promote the retention of moisture. The exchangeelements 4 extend transversely of the axis of the housing 1, beingretained on the ends of the housing by annular, inwardly-projecting endflanges 23 and 24. The external face 30 of each exchange element 4 islocated just rearwardly of a curved slot 31 formed between the end ofthe housing 1 and the respective end flanges 23 and 24. Each slot 31communicates with an oxygen conduit 32 extending longitudinally of theHME in a ridge 33 along the lower side of the housing 1. The spacebetween the external face 30 of the exchange elements 4 and the ends ofthe housing 1 helps protect the elements from contact and contamination.

Midway along its length, the ridge 33 is interrupted by a recess 40, ofa tapering shape, on the lower side of the exterior of the housing 1.The depth of the recess 40 is about half the width of the ridge 33, theoxygen conduit 32 continuing with a reduced width behind the recess,along the entire length of the housing 1 so that the slots 31 at bothends communicate with one another via the conduit. The recess 40 servesto house and protect the oxygen supply port 5.

The oxygen supply port 5 is formed by a stem 51 of circular externalsection and with a taper on its external surface such that its outer,free end 52 has a smaller diameter than its inner end 53. The port 5extends parallel to the patient coupling 2 in the opposite direction,that is, at right angles to the axis of the housing 1. The oxygen supplyport 5 is located in the recess 40 on the lower side of the housing andits length is such that it is entirely contained within the recess. Inmodifications of the HME, the oxygen supply port could project slightlyfrom the recess providing that the major part of its length wascontained within the recess. The space within the recess 40 around theoxygen supply port 5 is such as to enable a female coupling on the endof an oxygen supply tube (not shown) to be pushed onto and retained onthe port.

Oxygen supplied to the port 5 flows through the relatively narrowpassage through the port and opens into the section 32′ of the oxygenconduit 32. This space 32′ has a larger cross-sectional area (typicallyabout 13.4 mm²) than that of the passage through the oxygen port(typically about 3.1 mm²) thereby resulting in a drop in pressure as theoxygen flows out of the port 5 into the section 32′. The flow of oxygenis then abruptly diverted through 90° as it flows outwardly in bothdirections away from the port 5. This change in direction producesturbulence and a further drop in pressure. The oxygen then flows fromthe reduced width section 32′ into opposite ends of the main section 32and, because these have a larger cross-sectional area (typically about47.9 mm²) than the reduced width section, this results in a furtherreduction in the pressure of the oxygen. Oxygen flow from the port 5 inboth directions is substantially equal because of the central locationof the port and its symmetrical disposition. Oxygen flows along theconduit 32 and out of the slots 31 over the external surface 30 of thetwo exchange elements 4. In this way, the supplementary oxygen has topass through the exchange elements 4 before passing to the trachea, sothat it is warmed and moistened in the same way as the ambient air. Thereduced pressure caused by the geometry of the oxygen flow path from theport 5 to the external surfaces of the exchange elements 4 reduces theflow rate out of the slots 31 and ensures that a maximum proportion ofthe oxygen remains in the region of the exchange elements withoutflowing past them. This helps ensure the maximum efficiency of oxygenmixing with ambient air in the region of the exchange elements 4 andhence the maximum concentration of oxygen supplied to the patient.

The HME additionally has a suction access aperture 60 located directlyopposite the tracheal tube coupling 2. The aperture 60 is rectangularand is normally covered and closed by a cover or flap 61 formedintegrally with the housing 1 and attached with it at one end by a webor living hinge 62, which is bendable to allow the flap to be raised orlowered over the aperture. The edges of the flap 61 and the aperture 60are shaped such that the flap can snap into position in the aperture andprovide a substantially gas-tight seal. The free end 63 of the flap 61is curved away from the surface of the housing 1 to form a lip when theflap is closed by which it can be gripped and opened. When the patient'stracheal tube 3 needs suctioning, the clinician lifts the flap 61 andinserts the suction tube down the tracheal tube through the patientcoupling 2. This avoids the need to remove the HME. The fit of the flap61 in the aperture 60 could be arranged such that the flap can be blownoutwardly by increased pressure created by the patient, such as whencoughing. This would provide a pressure relief feature. The dimensionsof the suction aperture 60 are relatively large so that a suctioncatheter can be inserted through the aperture with minimal contact withthe edge of the aperture so as to minimize wiping the catheter andthereby reduce the risk that secretions on the outside of the catheterwill be removed and remain inside the HME. Preferably the width of theaperture 60 is at least substantially the same as the internal diameterof the tracheal tube 3 with which the HME is used, typically the widthis about 10 mm and the depth is about 16 mm. Suction catheters shouldhave an external diameter not greater than half the internal diameter ofthe tracheal tube, the maximum size of the suction catheter usuallybeing 16 F, that is 5.3 mm outside diameter, for use with a 10 mminternal diameter tracheal tube.

By locating the oxygen supply port in a recess where it is containedsubstantially entirely within the boundaries of the recess, in themanner described above, the HME can present a compact configuration andits surface is less likely to snag on adjacent tubes, dressings, wiresor the like when not in use.

The oxygen supply port need not be concealed within the recess whenconnected to the oxygen supply tube. Instead, the port could bedisplaceable from a position where it is concealed within a recess, whennot in use, to a position where it projects from the recess, when inuse.

In the arrangement shown in FIGS. 5 to 8, the oxygen supply port 105 hasan outer tapered portion 106 and a shorted, inner stem 107 projecting atright angles to the outer portion. As most clearly shown in FIG. 8, thestem 107 is solid and formed with a bifurcated toothed end 108, which isa snap fit in a hole 109 through the upper wall 110 of the recess 140into the interior 122 of the housing 101. One side of the stem 107 makesclose sliding contact in a concave cavity 146 formed in the cornerbetween a rear wall 147 and a side wall 148 of the recess 140 adjacentthe hole 109. The cavity 146 has a small opening 149 located towards therear wall 147 and opening through the wall into the conduit 132.

A passage 152 extends axially through the outer portion 106 of the port105 from the open, forward end 151 to a rear opening 153 formed in thewall of the stem 141. The oxygen supply port 105 is rotatable through90° about the axis of the stem 107, the fit of the toothed end 108 inthe hole 109 enabling the stem to rotate in the hole, whilst thefriction between the stem and the hole is sufficient to ensure that theport remains in whatever angular position to which it is displaced. Inthe stowed position shown in FIG. 5, the outer portion 106 extendsparallel to the axis of the housing 101 and parallel to its externalsurface, alongside the rear wall 147 of the recess 140. The length ofthe outer portion 106 locates in the recess 140 with just a small partof its width protruding so that the major part of the port 105 iscontained within the boundaries of the recess. In this position, thecurved surface of the stem 107 blocks any flow of gas through theopening 149. When the oxygen supply port 105 is stowed, as shown in FIG.5, the external surface of the HME is substantially uninterrupted byprojections so that it presents a compact, retracted configuration.

When the oxygen supply port 105 is swung clockwise through 90° (asviewed from below and as shown in FIGS. 6, 7 and 8) the outer portion106 extends outwardly at right angles to the axis of the housing 101 sothat the oxygen supply tubing can be connected to it readily. In thisposition, the rear opening 153 of the oxygen supply port 105 aligns withthe opening 149 so that oxygen can flow along conduit 132.

It is not essential for the oxygen supply port be displaceable betweenan extended and retracted position by rotation. As shown in FIG. 9, theport 105′ could be movable linearly in a slidable, telescopic fashion.In this arrangement, the port 105′ has an inner stem 141′ slidablymounted in a telescopic fashion on the outside of a short, radiallyextending tube 170 opening into the conduit 132′. The outer stem 142′extends at right angles to the inner stem 141′ in the same manner as inthe swivel port 105. The telescopic movement is such that, in itsretracted position, substantially all the port 105′ is contained withinthe boundaries of the recess 140′ whereas, when pulled out fully to itsextended position, the outer stem 142′ extends outside the recess 140′so that an oxygen supply connector can be fitted easily to the stem. Themounting of the inner stem 141′ on tube 170 could be such as either toprevent or to permit rotation of the port 105′. Where rotation isprevented, the outer stem 142′ would be confined to extend only parallelto the axis of the HME. Where rotation is permitted, the outer stem 142′would be free to swivel to any desired orientation once pulled out ofthe recess 140′. Because rotation of the port 105′ is not hindered bycontact with the sides of the recess 140′, when it is extended, it canbe free to rotate through 360°. The port 105′ could be arranged torestrict flow of gas through it when in the retracted position. Thiscould be achieved by means of a formation inside the port 105′ thatobstructs the end of the tube 170 when the port is retracted.Alternatively, the open end of the outer stem 142′ could be arranged tobe obstructed by a formation on the inside of the recess 140′ when inits stowed, retracted position. Instead of the inner stem 141′ embracingthe outside of the tube 170, alternative arrangements could have aninner stem extending inside a tube in a telescopic fashion. The portneed not be bent at an angle but could simply be straight, aligned withthe axis of telescoping movement. In such an arrangement, it might bedesirable for the port to be able to be locked in its extended positionso as to facilitate coupling to the oxygen tubing. This could beachieved by a pull-and-twist bayonet action. After use, the port wouldbe unlocked and retracted to its stowed position within a recess.

It will be appreciated that the invention is not confined to HMEs butcould be used with other devices such as where the gas-treatmentelements are filters.

1. A gas-treatment device having a housing, a first port adapted for connection to a patient breathing device, a gas-treatment element through which gas can flow in both directions to and from the patient and a second, oxygen supply port by which oxygen can be supplied to the patient via the gas-treatment device, the oxygen supply port being in the form of a tubular stem, characterized in that the housing has a recess on its external surface, and that the major part of the oxygen supply port extends within the recess when not in use.
 2. A device according to claim 1, characterized in that the device has two gas-treatment elements at opposite ends of the housing.
 3. A device according to claim 1, characterized in that the oxygen supply port is located intermediate the ends of the housing.
 4. A device according to claim 1, characterized in that the gas-treatment is an HME exchange element.
 5. A device according to claim 1, characterized in that the housing has an elongate shape and that the oxygen supply port extends substantially at right angles to the axis of the housing.
 6. A device according to claim 1, characterized in that the oxygen supply port is displaceable from a first position in which a major part of the port is contained within the recess and a second position in which it projects from the recess for connection of an oxygen supply tube.
 7. A device according to claim 6, characterized in that the oxygen supply port is displaceable by rotation.
 8. A device according to claim 6, characterized in that the oxygen supply port is displaceable by sliding.
 9. A device according to claim 1, characterized in that the housing has a suction aperture located substantially opposite the first port, and that the suction aperture is covered by a flap that can be displaced to enable a suction catheter to be extended through the suction aperture into the patient breathing device.
 10. A device according to claim 1, characterized in that an oxygen supply passage extends along the housing and opens onto an external face of the gas-treatment element, that the oxygen supply port is directed at an angle to the oxygen supply passage such that oxygen flow changes direction where it emerges from the port into the passage, and that the cross-sectional area of the oxygen passage is greater than that of the oxygen port so that oxygen pressure drops where it emerges from the port into the passage. 